This research will provide critical information regarding the initial efficacy and optimal doses of a novel drug combination, BUP and NTX, for COC dependence, which will enhance the probability of success when advanced to a clinical trial. Innovations of the proposed research include: 1) testing a combination of marketed drugs that demonstrated modest efficacy when tested as mono-therapies; 2) the use of a sophisticated drug self-administration procedure; 3) providing the impetus for the conduct of a Phase II clinical trial to further demonstrate the efficacy of BUP-NTX combinations for COC dependence; and 4) demonstrating the initial efficacy and optimal doses of a combination of commercially available drugs, as opposed to waiting for novel molecules to be available for testing in humans, thereby impacting clinical research and practice more quickly. In these ways, the proposed project will shift the current clinical research paradigm in pharmacotherapy development and have a significant impact on the treatment of COC dependence.